The development of matrix-assisted laser desorption/ionization (“MALDI”) and electrospray ionization (“ESI”) techniques has greatly increased the range of biomolecules that can be studied with mass analyzers. MALDI and ESI techniques allow normally nonvolatile molecules to be ionized to produce intact molecular ions in a gas phase that are suitable for analysis.
Both MALDI and ESI techniques are, however, rather “dirty” techniques in that a relatively large amount of the nonvolatile material that is vaporized can be deposited on the electrodes of the ion source and mass analyzer. Material deposition is of particular concern in high-throughput applications such as proteomics studies that seek to operate mass analyzer systems on a “24/7” basis.
Material deposition can produce a variety of problems. Material deposited on electrodes can, for example, charge up and produce uncontrolled potentials and distorted potentials on the electrodes. Such uncontrolled and distorted potentials on electrodes in the ion beam path can significantly decrease both mass analyzer sensitivity and mass analyzer resolution. In addition, such material deposition increases mass analyzer downtime by increasing the frequency with which electrodes need to be cleaned. A need therefore exists for ion sources that reduce or eliminate material deposition on electrodes in the ion beam path.
In many biomolecule studies (such as, e.g., proteomics studies) that employ mass analyzers the biomolecule masses of interest can readily span two or more orders. An ongoing desire therefore exists for ion sources and mass analyzers systems that can provide increased dynamic mass range.
In addition, in many biological studies there is a limited amount of sample available for study (such as, e.g., rare proteins, forensic samples, archaeological samples). Accordingly, there is an ongoing desire for ion sources and mass analyzers systems that can provide increased sensitivity and resolution and can thus operate with ever decreasing amounts of sample.